External Memory
External memory, also known as secondary memory, is a type of computer memory that is not directly accessible by the CPU (central processing unit) and is used for long-term storage of data and programs. Unlike primary memory, such as RAM and cache memory, external memory is non-volatile, meaning that its contents are retained even when the power is turned off.
There are several types of external memory devices, including hard disk drives (HDDs), solid-state drives (SSDs), optical storage devices (such as CD and DVD drives), USB flash drives, and memory cards. External memory devices are connected to the computer system via ports such as USB, SATA, or PCI-E.
HDDs and SSDs are the most common types of external memory used in modern computers. HDDs use magnetic disks to store data, while SSDs use flash memory. Both types of devices provide large amounts of storage capacity at relatively low cost, and they can be easily removed and replaced as needed.
Optical storage devices, such as CD and DVD drives, are less common than they used to be, but they are still used for archiving and distributing software, music, and movies. USB flash drives and memory cards are portable and convenient for transferring data between computers or for storing data on mobile devices such as smartphones and tablets.
The use of external memory is important for computer systems because it provides a way to store data and programs that can be accessed even when the computer is turned off or restarted. External memory devices are also useful for backup and disaster recovery, as they can be used to store copies of important data in case of a system failure or other catastrophic event.
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